Japanese Patent Application Laid-Open (JP-A) No. H09-76859 describes a vehicle seat in which a side airbag device is provided at a side section of a seatback. Explained briefly, in the technology described in this document, a side frame configuring part of a seatback frame is formed with a recess in which an inflator and a bag body configuring the side airbag device are stowed, and a seatback pad is attached to the side frame. The side airbag device is thus disposed between the side frame and the seatback pad. As viewed from a side of the seat, a slit forming three sides of a rectangle is formed in the seatback pad at a location at a side of the seat from the side airbag device. Deployment of the bag body to the side of the seat can accordingly be facilitated during actuation of the side airbag device, namely in a case in which gas generated by the inflator is supplied inside the bag body.